This invention relates to improvement in rotating drum wood incisors.
When wood boards are preservative treated it is desirable that beforehand perforations be cut at spaced intervals in their surfaces to aid in absorption of the preservative. Wood incisors having driven drums with protruding teeth are generally used for this purpose, with the board being rolled between two perpendicular sets of separated parallel pairs of the drums to form the perforations.
However, boards contain many minor irregularities or hard spots, such as knots, where the teeth will not penetrate to their normal depth. Since the prior art incisors have drums which are separated by a fixed amount, once initially adjusted to accommodate the particular dimensions of the board, problems arise when these irregularities or hard spots are encountered. In many instances the results of this situation is that one or more of the teeth will become broken.
Also it is not uncommon for boards having a small cross-section to become warped or curved. Again the prior art devices of this class are not capable of accommodating this condition and they try to straighten the board as it passes through the drums. As in the former situation, when this condition occurs the drums are subject to damage or tooth breakage.
Finally, the drums of the prior art devices have teeth which are individually installed on the core in a manner such that after extended use the fit of the teeth becomes loose causing breakage or loss of the teeth, and ultimately necessitating expensive replacement of parts. Also, the installation of teeth is a time-consuming operation resulting in considerable down-time of the device. Therefore, the prior art devices are run with broken teeth rather than replacing them as breakage occurs with an attendant loss of performance.